1. Field of the Invention
The present invention relates to a liquid ejection head setting a substantial length of a nozzle array for ejecting a liquid as long as possible.
2. Related Art
Although it is an effective method to prolong a length of a nozzle array orthogonal to a main scanning direction of an apparatus main body in order to increase printing speed, that is, to increase a printing area per unit time, a nozzle head cannot be used when malfunction is brought about even at a single nozzle opening in a fabrication procedure and therefore, a plurality of heads are aligned in a direction of a nozzle array to use.
However, by only arranging a plurality of ink ejection units A in a direction of aligning nozzles as shown by FIG. 17A, a dot nonforming area C is produced at an interval between nozzle arrays B of heads contiguous to each other.
In order to resolve such a problem, there has been proposed a recording head enabling long length formation excluding the above-described dot nonforming area C by arranging the ink ejection units A in a zigzag shape as is found also in Japanese Patent Publication No. 2752843 (FIG. 17B).
According thereto, although a long nozzle array without interruption in view from a sub scanning direction can be formed, there poses a problem that a size of simply adding widths of ink ejection units U is constituted, a dimension of an apparatus main body of a liquid ejection head in a main scanning direction is significantly enlarged, in order to make an ink ejection head effective, it is necessary to scan more than a width of a record medium and the apparatus is large-sized.
The invention has been carried out in view of such a situation and it is an object thereof to provide a liquid ejection head capable of realizing long length formation of a nozzle array while restraining an increase in a dimension of a liquid ejection head in a main scanning direction.
(1) In order to achieve the above-described object, the invention is constituted by a liquid ejection head constituting a liquid ejection unit by including a flow path unit formed by a laminated member including a nozzle plate formed with a nozzle array by aligning nozzle openings, a flow path forming plate formed with a pressure generating chamber communicating with the nozzle opening and a sealing plate for closing an opening of the pressure generating chamber, the liquid ejection unit being attached to a head holder for guiding a liquid from a liquid supply source, wherein at least two of first liquid ejection units are aligned in a first direction, a second liquid ejection unit having a length in the first direction shorter than a length in the first direction of the first liquid ejection unit is arranged at a discontinuous portion of the nozzle array present between the two first liquid ejection units in a state of being shifted from an alignment of the first liquid ejection unit in a second direction of an apparatus main body and a single unit is formed by the first liquid ejection units and the second liquid ejection unit such that the respective nozzle arrays constitutes a nozzle group for ejecting a same kind of a liquid.
That is, at least two of the first liquid ejection units are aligned in the first direction, the second liquid ejection unit having the length in the first direction shorter than the length in the first direction of the first liquid ejection unit is arranged at the discontinuous portion of the nozzle array present between the two first liquid ejection units in the state of being shifted from the alignment of the first liquid ejection unit in the second direction of the apparatus main body and the single unit is formed by the respective nozzle arrays to constitute the nozzle group for ejecting the same kind of the liquid by the first liquid ejection units and the second liquid ejection unit.
Thereby, the nozzle group for ejecting the same kind of the liquid is formed by the respective nozzle arrays of the first liquid ejection units and the second liquid ejection unit, a length of the effective nozzle array is apparently prolonged and ejection of the liquid to the fixed area is executed in a short period of time. Further, the first liquid ejection unit is a liquid ejection unit achieving an inherent ejection function and the second liquid ejection unit is for making the nozzle arrays of the two first liquid ejection units continuous in view of the function. Therefore, the first liquid ejection unit is assigned with a so-to-speak standard article having the most stabilized liquid ejection function, in contrast thereto, the second liquid ejection unit is provided with a length shorter than that of the first liquid ejection unit and therefore, the second liquid ejection unit per se is not provided with a factor of deteriorating the liquid ejection function and the long nozzle group having the stabilized liquid ejection function is provided for the first and the second liquid ejection units as a whole. Further, different kinds of liquids are ejected at the respective nozzle groups and therefore, by constituting a predetermined number of the nozzle groups, a number of kinds and a variety of liquid ejection can be carried out. When the above-described single unit is applied to the ink jet type recording apparatus, high speed formation of printing and a variety of print qualities are achieved.
(2) The invention is constituted such that the second liquid ejection units overlap each other in a direction orthogonal to the nozzle array in a state of shifting two of the single units in the first direction.
Thereby, the nozzle array of the second liquid ejection unit of other of the single units can be made proximate to the nozzle array of the first liquid ejection unit of one of the single units. Therefore, rows of the respective first liquid ejection units in the two single units can be made to be proximate to each other and shortening of a dimension of the liquid ejection head mounted with a plurality of the liquid ejection units in the second direction is realized. Specifically, although a unit space of an amount of four rows is needed when the two single units are not shifted as described above, a unit space of substantially an amount of three rows is constituted by the above-described alignment.
(3) According to the invention, an opposed unit is formed by opposingly arranging at least two of the single units in a state of being shifted from each other in the first direction to thereby arrange the respective second liquid ejection units in the respective single units substantially on a same row.
According thereto, the nozzle array of the second liquid ejection unit of other of the single units can mostly be made proximate to the nozzle array of the first liquid ejection unit of one of the single units.
Therefore, the rows of the respective first liquid ejection units in the two single units can be made to be mostly proximate to each other and shortening of the dimension of the liquid ejection head mounted with a plurality of the liquid ejection units in the second direction at a maximum is realized.
(4) According to the invention, a plurality of the opposed units are arranged.
According thereto, a number of the single units can be arranged while reducing the space in the second direction and therefore, sufficient kinds of liquids can be ejected from the prolonged nozzle groups by the compact liquid ejection head.
(5) According to the invention, a third liquid ejection unit for extending a total length of the nozzle group of the single unit by a predetermined length is incorporated in the single unit and the nozzle group is constituted by the respective nozzle arrays of the first, the second and the third liquid ejection units.
According thereto, the nozzle group can be set with a predetermined length by supplementing the length of the nozzle group pertinently by the third liquid ejection unit. Further, by making the length of the third liquid ejection unit in the first direction shorter than that of the first liquid ejection unit, the nozzle group can be prolonged while maintaining excellent function without deteriorating the liquid ejection function by the third liquid ejection unit.
(6) The invention is constituted such that the third liquid ejection unit includes a third liquid ejection unit arranged substantially at a row the same as the row of the second liquid ejection unit.
According thereto, the third liquid ejection unit can be arranged similar to “shifted arrangement” of the above-described second liquid ejection unit and therefore, even when the third liquid ejection unit is used, the liquid ejection head reducing the space in the second direction can be constituted.
(7) The invention is constituted such that the third liquid ejection unit includes the third liquid ejection unit arranged on the row substantially the same as the row of the second liquid ejection unit and includes a third liquid ejection unit arranged at a row substantially the same as a row of the first liquid ejection unit.
According thereto, the third liquid ejection unit arranged at the row the substantially the same as the row of the second liquid ejection unit achieves a function of extending the nozzle group in a state of being shifted from the first liquid ejection unit in the second direction. Further, the third liquid ejection unit arranged at the row substantially the same as the row of the first liquid ejection unit achieves a function of extending the nozzle group in a state of the row substantially the same as the row of the first liquid ejection unit by way of the third liquid ejection unit in the above-described shifted state. Therefore, the third liquid ejection unit extends the nozzle group in two kinds of modes of a state of being shifted in the second direction and a state of the row substantially the same as the row of the first liquid ejection unit and extension of the nozzle group having a high degree of freedom can be carried out by pertinently selecting the shifted state of the former and the state of the same row of the latter.
(8) The invention is constituted such that lengths of all of the third liquid ejection units and the second ejection unit in the first direction are substantially the same.
According thereto, all of the second and the third liquid ejection units can be made common as unit parts and therefore, the invention is advantageous in a reduction of a kind of parts and a reduction in cost.
(9) According to the invention, end portions of the nozzle groups between a plurality of the single units are arranged to align substantially on a straight line in the second direction of the apparatus main body by presence of the third liquid ejection unit.
According thereto, even when a shift is produced at the end portion of the nozzle group by arranging to shift the single unit formed by the first and the second liquid ejection units, the shift can be corrected to align substantially on the straight line by arranging the third liquid ejection unit. Therefore, liquid ejection without shift can be carried out among the plurality of the single units.
(10) The invention is constituted such that the nozzle arrays of the single units contiguous to each other in view from the second direction of the apparatus main body are arranged such that an opening pitch of the nozzle array of other of the single units is shifted from an opening pitch of the nozzle array of one of the single units and an amount of the shift is an amount of a half of the opening pitch.
According thereto, when two of the nozzle arrays in the shifted relationship are made to be compound in the second direction, the opening pitch becomes the substantially small opening pitch. Here, when the so-to-speak half pitch is constituted as described above in the nozzle array the opening pitch of which is reduced, liquid ejection per unit area to a member subjected to the liquid ejection is brought into an extremely dense state. On the other hand, when the half pitch is constituted as described above in the nozzle array the opening pitch of which is comparatively increased, by making the half pitch a multiplication of an integer of resolution, a number of times of strokes of the liquid ejection head in the second direction can be reduced. As advantages of these, in the ink jet type recording apparatus the former is effective in ensuring fine ejection quality and the latter can achieve shortening of printing time by being utilized in draft printing or the like.
(11) According to the invention, the head holder is provided with a projected portion for positioning the first liquid ejection unit, the second liquid ejection unit, the third liquid ejection unit or the like.
According thereto, by attaching the respective liquid ejection units to the head holder by being brought into contact with the projected portion for positioning, the single unit and the nozzle group can be formed with high accuracy and excellent liquid ejection is achieved from the prolonged nozzle group. Further, stabilized liquid ejection is achieved by the opposed unit opposing the single units as a whole. Further, even when the nozzle arrays of the single units contiguous to each other are shifted to make a half pitch of the nozzle openings as described above, the highly accurate opening pitch can be ensured.
(12) According to the invention, the head holder is provided with an outer peripheral wall member for positioning the first liquid ejection unit, the second liquid ejection unit, the third liquid ejection unit or the like.
According thereto, by attaching the respective liquid ejection units to the head holder by being brought into contact with the outer peripheral wall member for positioning, the single unit and the nozzle group can be formed with high accuracy and excellent liquid ejection is achieved from the prolonged nozzle group. Further, stabilized liquid ejection is achieved in the opposed unit opposing the single units as a whole. Further, even when the nozzle arrays of the single units contiguous to each other are shifted to constitute the half pitch of the nozzle openings, the pitch of the highly accurate nozzle opening can be ensured.
(13) The invention is constituted such that the first liquid ejection unit, the second liquid ejection unit, the third liquid ejection unit or the like is constituted by bonding the flow path unit to the head case, a pressure generating element for producing a pressure variation in the pressure generating chamber is constituted by a piezoelectric oscillator of a vertical oscillation mode, the piezoelectric oscillator is fixed to a fixing board, the piezoelectric oscillator and the fixing board are inserted into a containing chamber provided at the head case in a state of corresponding to the pressure generating chamber and the fixing board is brought into a fixed state at inside of the containing chamber.
According thereto, the piezoelectric oscillator per se of the vertical oscillation mode is excellent in operational response to the applied drive signal, further, driving displacement output in the vertical direction is provided and therefore, the liquid in the pressure generating chamber is pressurized to correspond to the drive signal and liquid ejection from the nozzle array is firmly carried out with high reliability. The respective first, second and third liquid ejection units can be made to function by the piezoelectric oscillator having such a property and therefore, liquid ejection from a series of the nozzle groups can excellently be achieved in any of the nozzle arrays. Therefore, an amount of the liquid droplet and accuracy of impacting the liquid droplet can be confined to levels which are not problematic in view of practice over a total area of the length of the prolonged nozzle group.